Having just installed the BMB pads, you gotta get them hot when you do break in... But when you do, you'll know it. If you're doing it right, the 5th or 6th stop, you'll wonder why they aren't working as well. That is called brake fade and it's a symptom of a hot braking system.
The pads only solution is good for the emergency stop. You've got the power and grip to stop big tires. I can lock up the 35s with the BMB pads. If you want to do better and get less fade, the big brake kit is the way to go. It is necessary? Who knows. If you're in crazy rush hour traffic and hauling yourself down from 50 mph to 5 mph all the time and notice your brake fading, then yeah, get the BBK. For routine driving, light traffic, going a mile between stops so the brakes have time to cool, the pads are probably all you need.